Add more doc comments

backend.go

@@ -4,18 +4,26 @@ import "sort"
 import "image"
 import "errors"
 
+// Backend is any Tomo implementation. Backends handle window creation, layout,
+// rendering, and events so that there can be as many platform-specific
+// optimizations as possible.
 type Backend interface {
+	// These methods create new objects. The backend must reject any object
+	// that was not made by it.
 	NewWindow       (image.Rectangle) (MainWindow, error)
 	NewBox          () Box
 	NewTextBox      () TextBox
 	NewCanvasBox    () CanvasBox
 	NewContainerBox () ContainerBox
 
+	// Run runs the event loop until Stop() is called, or the backend
+	// experiences a fatal error.
+	Run () error
+	
 	// Stop must unblock run.
-	Run  () error
 	Stop ()
 
-	// Do performs a callback function in the main thread as soon as
+	// Do performs a callback function in the event loop thread as soon as
 	// possible. This method must be safe to call concurrently.
 	Do (func ())
 }

object.go

@@ -16,6 +16,8 @@ type Side int; const (
 	SideLeft
 )
 
+// Inset represents a rectangle inset that can have a different value for each
+// side.
 type Inset [4]int
 
 // I allows you to create an inset in a CSS-ish way:
@@ -84,11 +86,13 @@ func (inset Inset) Vertical () int {
 	return inset[SideTop] + inset[SideBottom]
 }
 
+// Border represents a single border of a box.
 type Border struct {
 	Width Inset
 	Color [4]color.Color
 }
 
+// Align lists basic alignment types.
 type Align int; const (
 	AlignStart Align = iota // similar to left-aligned text
 	AlignMiddle             // similar to center-aligned text

tomo.go

@@ -43,32 +43,38 @@ func Stop () {
 	backendLock.Unlock()
 }
 
+// Do performs a callback function in the event loop thread as soon as possible.
 func Do (callback func ()) {
 	backendLock.Lock()
 	if backend != nil { backend.Do(callback) }
 	backendLock.Unlock()
 }
 
+// NewWindow creates and returns a window within the specified bounds on screen.
 func NewWindow (bounds image.Rectangle) (MainWindow, error) {
 	assertBackend()
 	return backend.NewWindow(bounds)
 }
 
+// NewBox creates and returns a basic Box.
 func NewBox () Box {
 	assertBackend()
 	return backend.NewBox()
 }
 
+// NewTextBox creates and returns a Box that can display text.
 func NewTextBox () TextBox {
 	assertBackend()
 	return backend.NewTextBox()
 }
 
+// NewCanvasBox creates and returns a Box that can display custom graphics.
 func NewCanvasBox () CanvasBox {
 	assertBackend()
 	return backend.NewCanvasBox()
 }
 
+// NewContainerBox creates and returns a Box that can contain other boxes.
 func NewContainerBox () ContainerBox {
 	assertBackend()
 	return backend.NewContainerBox()